Abarim Publications' online Biblical Hebrew Dictionary
The root נמר (nmr) isn't used as verb in the Bible and it's not clear what it may have reflected to the Hebrews. In Arabic a comparable root describes purity of water and in Assyrian it means to shine or gleam.
In the Bible only one derivation occurs, namely the masculine noun נמר (namer), denoting the leopard, and it's obviously also not quite clear for what exactly the leopard was known for to the Hebrews.
Our noun occurs five times. Twice the leopard is reckoned for its propensity to ambush its prey (Jeremiah 5:6 and Hosea 13:7), once for its speed (Habakkuk 1:8), once for its spotted fur (Jeremiah 13:23) and once for its beauty (or so it seems: Song of Solomon 4:8).
The prophet Isaiah predicts the harmony of the new world, and foresees the leopard reposing with a goat kid (Isaiah 11:6).